1. Field of the Invention
The invention relates to a polyethylene terephthalate, and more particularly to a catalyst for polyethylene terephthalate polymerization and a composite material formed by the polyethylene terephthalate polymerization.
2. Description of the Related Art
Polyethylene terephthalate (PET) has been popularly utilized for food and drink packages, having an annual growth rate of about 15 to 20%. PET containers have largely replaced PVC bottles and metal cans.
One of the PET forming methods is reversible bis-hydroxy ethylene terephthalate (BHET) polymerization. Ethylene glycol is removed by increasing the reaction temperature to control the molecular weight of the PET. However, PET degradation occurs as the reaction period increases. To reduce the reaction period, generally, a heavy metal catalyst is added to advance polymerization. However, residual heavy metal catalyst in the PET products is harmful to the health of mammals, especially when applied for food or drink packages. Thus, development of rapid PET polymerization without the addition of heavy metal catalysts is desirable.
Additionally, development of a PET material with high mechanical property, low linear expansion coefficient, high barrier, high thermal stability, high flame retardancy and/or high transparency is also popular. Generally, nano-level inorganic materials are blended into the PET to form nano-level composite materials. However, nano-level inorganic material aggregation often occurs, resulting in uneven blending, deteriorating product quality. Thus, development of a method for uniformly blending the nano-level inorganic material into the PET to form a nano-level composite material is desirable.